尝试定义 FOREIGN KEY 时出现“表中不存在键列”

Posted 2023-05-08

【中文标题】尝试定义 FOREIGN KEY 时出现“表中不存在键列”

【英文标题】："Key column doesn't exist in table" when trying to define FOREIGN KEY

【发布时间】：2012-11-06 19:16:26

【问题描述】：

我正在尝试设置一个创建 5 个表的 mysql 脚本。在三个表中，有一个FOREIGN KEY，并且对于所有三个表都会出现相同的错误：

Error Code: 1072. Key column ... doesn't exist in table

而 ... 是 Gebaeude、Dept_Name 和 Mat_Nr

这是脚本

use cs261_24;

drop table if exists Professor;
drop table if exists Departement;
drop table if exists Gebaeude;
drop table if exists Student;
drop table if exists Pruefung;


CREATE TABLE Gebaeude (
                        Gebaeude    VARCHAR(20) NOT NULL PRIMARY KEY,
                        Hauswart    VARCHAR(20) NOT NULL,
                        Adresse     VARCHAR(20) NOT NULL
)engine = innodb;

CREATE TABLE Professor  (
                        P_ID        INTEGER PRIMARY KEY CHECK (P_ID > 0),
                        P_Name      VARCHAR(20) NOT NULL,
                        Dept_Name   VARCHAR(20) NOT NULL,
                        Raum        INTEGER UNIQUE CHECK (Raum > 0),
                        Tel         INTEGER(10) UNIQUE CHECK (Tel > 210000000),
                        FOREIGN KEY (Gebaeude) REFERENCES Gebaeude (Gebaeude) 
)engine = innodb;

CREATE TABLE Departement (
                        Dept_Name   VARCHAR(20) NOT NULL PRIMARY KEY,
                        Vorsteher   VARCHAR(20) NOT NULL
)engine = innodb;

CREATE TABLE Student (
                        Mat_Nr      INTEGER(8) PRIMARY KEY CHECK (Mat_Nr > 0),
                        S_Name      VARCHAR(20) NOT NULL,
                        Semester    INTEGER CHECK(Semester > 0),
                        FOREIGN KEY (Dept_Name) REFERENCES Departement (Dept_Name) 
)engine = innodb;

CREATE TABLE Pruefung (
                        Pr_ID       INTEGER PRIMARY KEY CHECK(Pr_ID > 0),
                        Fach        VARCHAR(20) NOT NULL,
                        Pruefer     VARCHAR(20) NOT NULL,
                        Note        FLOAT CHECK (Note >= 1 AND Note <= 6),
                        FOREIGN KEY (Mat_Nr) REFERENCES Student (Mat_Nr)
)engine = innodb;

为什么？我使用 MySQL Workbench，我清楚地看到创建的表，以及特定的列被标记为主键！

【参考方案1】：

你做错了，看看这个例子

http://www.sqlfiddle.com/#!2/a86cf

您的 FK 行应该更像这样：

FOREIGN KEY (field_that_will_be_Fk) REFERENCES Table_to_reference (field_to_reference)

I.E=

CREATE TABLE Gebaeude (
                        Gebaeude    VARCHAR(20) NOT NULL PRIMARY KEY,
                        Hauswart    VARCHAR(20) NOT NULL,
                        Adresse     VARCHAR(20) NOT NULL
)engine = innodb;

CREATE TABLE Professor  (
                       Gebaeude_FK varchar(20) NOT NULL,
                        P_ID        INTEGER PRIMARY KEY CHECK (P_ID > 0), 
                        P_Name      VARCHAR(20) NOT NULL,
                        Dept_Name   VARCHAR(20) NOT NULL,
                        Raum        INTEGER UNIQUE CHECK (Raum > 0),
                        Tel         INTEGER(10) UNIQUE CHECK (Tel > 210000000),
                        FOREIGN KEY (Gebaeude_FK) REFERENCES Gebaeude (Gebaeude) 
)engine = innodb;

【参考方案2】：

您必须先在每个表中创建列，然后才能将它们限制为外键。

参考此链接：Link